Bicycle brakes include hand brakes mounted to the handle bars of a bicycle. The hand brake usually includes a circular mounting portion which surrounds the handle bar, and which supports a main housing. The main housing usually supports a brake lever pivotally mounted to the main housing. The main housing may engage an annular brake cable assembly in a manner to allow the brake lever to pull the center brake cable with respect to the outer brake cable.
In most bicycles, the inner brake cable is connected directly to a point on the brake lever. In this instance, the angular displacement of the pivoting action of the lever translates into a proportional closing of the brake shoes against the wheel rim. There may be some trigonometric effect since the inner cable is being pivoted away from a support point in the brake lever housing. However, since the inner brake cable is supported at a constant radius from the pivot point, this effect in a standard system is not as pronounced.
In more specialized systems, there exists the possibility to increase the mechanical advantage to be applied to the brake cable. This is accomplished by reducing the radial distance between the end of the inner brake cable being pulled and the axis of pivot of the brake lever. In one known configuration, a series of spacers may selectively removed to enable a reduced radius. However, the user cannot adjust the system during the riding of the bicycle. This situation is potentially dangerous since the brake system of a bicycle becomes more loosely linked over time. The brake pads wear, the brake cable and associated hardware can become stretched if the brakes are applied too strongly. If any of the brake system changes during a ride such that brake lever displacement becomes insufficient to engage the brakes, the rider will have lost a portion or all of his braking ability.
Further, the use of removable inserts enables only discrete adjustment. Removal of one insert may immediately make the braking system too lax and eliminate braking ability, forcing a re-adjustment of the braking system. If the braking system becomes too lax, and if the user has the luxury of re-adjusting the system, the overall range of pull available to the system will still be limited.
Another system which is known uses a set screw to force a second pivoted fitting outward to force the brake cable to be pulled from a radially fixed perspective as the brake lever is depressed. This system is not adjustable by the rider during operation of the bicycle and requires a hexagon wrench since it is a hard adjustment of a set screw which bears against a portion of the brake lever. The device cannot be adjusted to give a smaller radial distance from the point of cable pull to the point of pivot. Thus, adjustability extends from a starting point of minimum adjustment to a maximum radius of the cable pull to the point of pivot. Further, adjustment to maximum has been shown to lift the point of cable pull too far from the point of pivot, and to cause the cable connect fitting to interfere with the brake lever housing.
Another prior art device is described in U.S. Pat. No. 5,448,927 and entitled "Adjustable Leverage Brake Lever" and issued to Wayne R. Lumpkin on Sep. 12, 1995. This device enables the pull point of the brake cable to be adjusted radially with a threaded bolt to any one of a number of fixed radial positions which are adjustable to be closer to or farther from the pivot point. The central problem with this device is that it does not allow the brake cable to return to a position which would leave the brakes in the maximum open position. Thus, where the adjustment is positioned to increase the mechanical advantage, it also reduces the range of travel of the brake cable from both its maximally extended and maximally retracted positions and toward the midpoint of the two extremes. This disenables the brakes from assuming the maximum open position and can cause unwanted rubbing of the brake shoe on the rim.
What is therefore needed is a braking system which will allow adjustment during riding to insure that the rider has maximum brake control and to insure that the rider will always be able to adjust the brakes to insure that full braking may be applied before the brake lever is limited in its travel by the handle bar. The system should not have significant resistance to adjustment of the brake, and should operate as smoothly and as effortlessly as possible.